1. Field of the Invention
The present invention relates generally to pipe couplings, where pipes are to be connected in abutting sections. More specifically, it relates to an improved coupler that obviates any need of threads on the pipe itself and of corresponding threads in the coupler.
2. Description of Related Art
In the past, the piping field of endeavor generally and in particular, the fire protection industry, has used three conventional piping methods: (1) threaded, (2) welded, and (3) flanged and bolted. Advent of a groove pipe method changed the fire protection industry by virtually eliminating the above mentioned three conventional piping methods for piping in nominal sizes of two and one half inches and larger.
Currently, the fire suppression industry mostly continues to use the threaded pipe method for screw fittings of nominal sizes of two inches and smaller. Over the years various non-threaded pipe connectors were introduced into the industry. The fittings were installed on plain ends of pipe two inches and smaller. These concepts were implemented in an attempt to reduce the cost of time and labor for the dominant threaded systems. All prior art plain end fitting retaining devices which attach to the pipe are concealed inside the coupling housing. All of these plain end pipe connections require internal pipe stops cast inside the fitting housing.
All of these methods force the outside surface of the pipe inwardly when cutting or crimping. Our conclusion is that the continued use of the threaded pipe method is due to the fact that the non-threaded pipe connecting systems have been found to be less secure and therefore not as reliable as the threaded method. That is, pipes were retained by setscrews, which have a propensity to become loose over time. When they are sufficiently loose, internal pressure forces the pipe out of sealed engagement with the coupler. This is known in the fire suppression industry as "blowout". In wet systems such as pressurized fire suppression systems, a considerable amount of water could be discharged onto occupied or otherwise utilized premises. This resulted both water related damage and loss of effective pressure in the fire suppression system.
Devices for connecting pipe are old and well known in the art. U.S. Pat. No. 4,397,485, issued to Sherman L. Wood on Aug. 9, 1983, describes a pipe connector which secures two axially aligned pipes with setscrews bearing perpendicularly against each pipe. No threading is required to connect the two pipes. However, Wood's device is susceptible to blowout. By contrast, the coupler of the present invention engages the two aligned pipes by interference fit established by clamps and secured by threaded fasteners. The clamps act in a direction urging each of the two principal pipes against the coupler. The present invention utilizes pipes having male grooves for enabling interference with the clamps. In accordance with conventional terminology, the term male groove used herein will be taken to mean, on a pipe having an inner radius and an outer radius, a groove having an external radius greater than the outer radius of the pipe. Satisfactory seating of the clamp is readily verified by observation in the present invention. By contrast, effective tightening of setscrews disposed perpendicularly to the pipe cannot be readily observed in the environment of ceiling mounted piping systems.
U.S. Pat. No. 3,402,945, issued to Howard E. Rittenhouse on Sep. 24, 1968, describes a clamped fitting which cooperates with a male grooved pipe. However, the two fittings shown in Rittenhouse are not configured to enable coaxial connection of pipes, threaded fitting of a third pipe, and use of a resilient seal, all being features of the present invention.
U.K. Patent Number 18,808, dated Nov. 11, 1893, describes clamped, coaxial engagement of abutting pipes. However, one pipe has an flared opening for receiving the end of the other, unlike the present invention. Also, the pipes of the U.K. patent do not employ male grooving. An elastic seal is provided in the U.K. patent, but this seal s axially compressed upon tightening the clamp. By contrast, the present invention provides an elastic seal which is radially expanded by insertion of a pipe into the novel coupler, and which seal is not subjected to compressive forces when the clamp is tightened.
U.K. Patent Application Number 411,087, dated Jun. 28, 1934, describes a fitting which secures two male grooved pipes by clamps. However, the U.K. device does not include an elastic seal disposed within the passage of the body of the device, whereas the present invention employs such a seal. Sealing in the U.K. patent is accomplished by deforming the pipe under compression against the body. This requires that the pipe be significantly softer than the fitting, the fitting being utilized with copper or other soft or malleable pipes. The present invention succeeds regardless of malleability or softness of the pipes.